Multi-function telescope

ABSTRACT

A telescope which simultaneously receives a plurality of frequency-distinguishable radiation transmissions from an object and which coaxially transmits one of said frequencies through a single aperture. The apparatus essentially consists of a double Cassegrainian telescope including an apertured primary objective reflecting mirror, an apertured secondary mirror and a filter element disposed between said mirrors for passing radiation at one of said frequencies through the aperture in the primary mirror and for reflecting radiation at a second of said frequencies through the aperture in the secondary mirror.

[451 Oct. 17, 1972 United States Patent Nelson [54] MULTI-FUNCTIONTELESCOPE 72 Inventor: Harry Nelson, Los Angeles, Calif. Examim-BenjaminAssistant Examiner-N. Moskowitz Assigneel c l zf aircraft p y CulverAttorney-Ernest L. Brown and W. H. MacAllister, .lr.

ity, a l

[57] ABSTRACT A telescope which simultaneously receives a plurality [22]Filed: Aug. 11, 1969 [2l] Appl. No.: 849,220

of frequency-distinguishable radiation transmissions from an object andwhich coaxially transmits one of said frequencies through a singleaperture. The apparatus essentially consists of a double Cassegrainiantelescope including an apertured primary" objective reflecting mirror,an apertured secondary mirror and a [56] References cued filter elementdisposed between said mirrors for UNITED STATES PATENTS passingradiation at one of said frequencies through the aperture in the primarymirror and for reflecting radiation at a second of said frequenciesthrough the aperture in the secondary mirror.

2,953,059 9/1960 Rodman et al. ...............356/5 3,204,102 8/1965Hand, Jr....................356/l4l 3,515,480 6/1970 Altman et al 356/43,519,829 7/1970 Pradel et al....................356/4 9 Claims, 4Drawing Figures MULTl-FUNCTION TELESCOPE BACKGROUND OF THE INVENTION 1.Field of the Invention ,The present invention relates to amulti-function telescope, and more particularly, this invention relatesorder to acquire and track a target.

The output beam of the laser is not sufficiently narrow in beam widthand must be processed through a collimating telescope. The lightreflected from the target is gathered and filtered to reduce the effectof scattered light in a second large apertured telescope. An infraredtracking system is required to assure that the laser is pointed towardthe desired target. Each of these components require separate aperturesand optical elements which must be assembled and maintained with theoptical axis of the elements in very close alignment. It is somewhatdifficult to achieve consistent accuracy in pointing the laser at atarget in the multi-apertured devices presently available.

OBJECTS AND SUMMARY OF THE INVENTION Therefore, an object of the presentinvention is to provide a smaller and more compact assembly of opticallyaligned elements.

Another object of this invention is the provision of a plurality ofoptical functions in a single telescopic barrel.

A further object of the invention is to simultaneously receive two formsof radiation through a single aperture and to provide radiationtransmission coaxially with the receiver aperture.

Yet another object of this invention is to provide a range finder whichreceives infrared tracking and laser ranging radiation in a singleaperture.

These and other objects and many attendant advantages of the inventionwill become apparent as the description proceeds.

The multi-function telescope according to the invention includes anoptical barrel supporting a series of elements on a common optical axis.A multi-output receiver telescope comprises a primary objectivereflector having a central aperture, a secondary convex reflector havinga central aperture positioned between the image point of the primaryreflector and the primary reflector so as to reflect the image rays backtoward the primary reflector aperture. A filter element is disposedbetween said primary and secondary reflectors for passing frequency of afirst radiation through the primary reflector aperture and reflectingradiation of a second frequency through the secondary reflectoraperture. Output of the second frequency radiation may be provided bydisposing said orthogonal element so as to deflect the radiation passingthrough the secondary reflector in a path normal to the optical axis ofthe barrel.

A transmitter telescope may be disposed forward of the secondaryreflector by providing an orthogonal element for reflecting transmitterradiation into a central coaxial bundle of rays which may be collimatedby a collimating lens coaxially disposed in the telescope barrel. Themulti-function telescope is readily adaptable to many uses such as alaser-IR ranging or tracking system comprising a multi-functiontelescope according to the invention. A laser is disposed to providepulses of secondary radiation directed toward said deflecting elementand projected through said collimating lens. A laser detector isdisposed to receive the secondary radiation orthogonally deflected bysaid deflecting element. The system further includes an infrareddetector disposed in front of the output aperture in said primarymirror. A digital counter is connected to the Q- switching section ofthe laser and to the laser detector. The infrared detector is utilizedto track the target. When the telescope is targeted, the laser is tiredand the Q-switch starts the counter. The signal from the laser detectorterminates the count to provide a digital signal indicative of rangewhich may be utilized for fire control or other purposes.

The invention will now become better understood by reference to thefollowing detailed description when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of amulti-function telescope according to the invention;

FIG. 2 is a view taken along the line 2-2 of FIG. 1;

FIG. 3 is an optical schematic view in perspective of the telescopeillustrated in FIG. 1; and

FIG. 4 is a schematic view of an IR-laser ranging system according tothe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2,the multi-function telescope 10 illustrated includes provision forsimultaneous reception of two forms of radiation and radiationtransmission coaxially with the receiver aperture. A single telescopebarrel 12 has a receiver aperture end 14 and an input aperture 16provided along the side of the barrel 10 in the vicinity of a primaryradiation output aperture 18.

A secondary radiation aperture 20 is provided at the other end of thebarrel through the axial bore of an annular primary objective reflector22. A flange 24 is joined to this end of the barrel 10. An apertured endmember 26 is fastened to the flange 24. The end member 26 includes arelieved outer section 28 fonning a lip engaging the flange 24. A hollowconical tube portion 30 is jointed to the aperture of the end member andextends inwardly.

The aperture 20 in the primary reflector 22 is inserted over the tube 30and is supported between the conical tube 30 and the inner wall 32 ofthe barrel 10. A retaining band 34 surrounding the tube 30 may beutilized to maintain the reflector 22 in position. The inner end surfaceof the tubing is received to fonn a seat for a selective filter element36. The filter 36 selectively passes one form of radiation and reflectsthe other. Suitably the filter may contain a dichroic coating 38.

A secondary reflector 40 having an aperture 42 is mounted in the backend of an internal coaxially supported barrel 44. An inwardly facingboss 45 formed near the back end of the barrel forms a stop for thereflector 40. The barrel 44 is centrally supported by means of a seriesof thin ribs 46 attached to the inner wall 32 of the barrel. The ribsterminate in hollow pin receiving cylinder 48 and may be alignedadjacent aperture flanges 50 extending from the inner barrel 44.'

Insertion of pins 52 through the flanges 50 into the cylinders 48completes the assembly.

The barrel further contains a prism 54 having a reflecting surface 56disposed behind the aperture 42 in secondary reflector 40. A seatingring 58 may be installed surrounding the forward endof the prism. Theinner barrel 44 further contains an aperture 57 facing aperture 16 andaperture 59 facing aperture 18. The forward end of the barrel tapersoutwardly and receives a collimating lens 60.

Referring now to FIG. 3, a transmitting telescope is formed by lens 66,prism 68, prism 54 and collimating lens 60. A light source such as laser62, emits a beam 64 which is broadened in lens 66, and reflected byprism 68 through input aperture 16 onto a silvered reflecting face ofprism 54. The beam 64 is collimated by lens 60 and can be projected by afield of view scan mirror 70. The prism 54 and lens 60 of thetransmitting telescope fit compactly into the core space not utilized ina Cassegrainian type of mounting.

The annular space 72 in the aperture is then utilized to receive twoforms of radiation from an object such as the reflected laser beam andinfrared energy emanating from a target in a ranging application. Thelaser and infrared light beam emanating from the object is deflected offfield of view scan mirror 70 into the annular space 72. The beam isreflected by primary reflector 22 onto the face of secondary reflector40. The secondary reflector 40 further reflects the beam onto thedichroic filter element 36. The infrared component of the beam is passedand leaves the telescope through the aperture in primary reflector 22and is deflected by an IR scan mirror 74 to further processingapparatus.

The laser component is reflected by the dichroic element 36 through theaperture 42 in secondary reflector 40 onto the external silvered face 56of prism 54. The face 56 is disposed to deflect the received laser beamthrough the primary radiation output aperture 18 onto a mirror 76 whichdeflects the beam onto a photoresponsive element or other suitabledevice.

Referring now to FIG. 4, a ranging system is illustrated incorporating amulti-function telescope according to the invention. The ranging systemcomprises a telescope 100 having a combined laser beam transmitting andradiation receiving annular, coaxial aperture 102. The received mixed IRand laser radiation beam is resolved and emitted from the telescopethrough a first axial IR receive aperture 104 and a second transverselaser receive aperture 106. A further transverse aperture 108 isprovided for introduction of laser light.

The system further includes an IR detector 110, a laser 112, a laserpulse source 114, a laser detector 116 and a digital counter 118. TheQ-switching section 134 of the laser is connected to the starting switchof the counter 118 and the terminating switch of the counter l 18 isconnected to the laser detector 116.

The telescope contains a primary apertured objecsignal of the laser asindicated in the laser detector 116 terminates the count. This resultsin a digital count that can be directly calibrated in distance.

The telescope of the invention will also find use in surveying, firecontrol systems, bombing systems and the like. It is to be understood,therefore, that only preferred embodiments of the invention have beendisclosed and that numerous substitutions, alterations and modificationsare permissable without departing from the scope of the invention.

What is claimed is:

1. A multi-function telescope comprising:

a housing means having an aperture for receiving a beam containing atleast two forms of radiation; means mounted within said housing meansfor concurrently resolving said beam into an axial component of one ofsaid forms of radiation and a nonaxial component of said other form ofradiation;

an annular concave primary reflector and an annular obtuse secondaryreflector positioned to reflect said axial component through the bore ofsaid annular primary reflector;

transmitting means coaxially disposed within said telescope fordirecting a beam of one of said forms of radiation outward through saidaperture;

a non-axial aperture formed in said telescope;

a filter transparent to said axial component and reflective to saidnon-axial component; and

a non-axial radiation deflector disposed in a position to cause saidnon-axial component to be reflected axially from said filter, throughthe bore of said secondary .reflector onto said deflector and out saidnon-axial aperture of said telescope.

2. A multi-function telescope comprising:

a housing means having a single receive aperture for receiving a beamcontaining at least two forms of radiation;

means mounted within said housing means for resolving said beam into anaxial component of one of said forms of radiation and a non-axialcomponent of said other form of radiation;

an annular primary reflector and a secondary reflector positioned toreflect said axial component through the bore of said annular primaryreflector;

transmitting means coaxially disposed within said telescope fordirecting a beam of one of said forms of radiation through said receiveaperture.

a non-axial aperture formed in said telescope;

a dichroic filter transparent to said axial component and reflective tosaid non-axial component, said secondary reflector including a centralpassage; and

a non-axial radiation deflector disposed behind said passage in aposition to cause said non-axial component to be reflected from saidfilter, through said passage onto said deflector and out said nonaxialaperture of said telescope.

3. A telescope according to claim 2 in which said housing comprises acylindrical outer barrel.

4. A telescope according to claim 3 further including an inner barrel,means for mounting said secondary reflector and deflector within saidinner barrel and means for coaxially mounting said inner barrel withinsaid outer barrel.

5. A telescope according to claim 4 in which said inner barrel furtherincludes a transmission radiation collimating lens disposed between saiddeflector and receive aperture.

6. A multi-function telescope comprising:

an optical barrel having a single receiving aperture;

an annular primary objective reflector means mounted in the end of saidbarrel opposite to said aperture and said reflector including a firstoutput aperture;

a secondary annular reflector defining a central passage disposed beforethe image point of said primary reflector and adapted to reflect theradiation from the primary reflector through the first output aperture;and

radiation resolving means disposed between said primary and secondaryreflectors transparent to one form of radiation and reflective toanother form and adapted to pass said one form through said first outputaperture and reflect said second form through the passage in saidsecondary mirror.

7. A multi-function telescope comprising:

an optical barrel having an axial receiving aperture and a transverseoutput aperture;

an annular primary objective reflector means mounted in the end of saidbarrel opposite to said receiving aperture, and said reflector includinga first axial output aperture;

a secondary annular reflector defining a central passage disposed beforethe image point of said primary reflector and adapted to reflect theradiation from said primary reflector through said first axial outputaperture;

deflection means mounted axially behind saidpassage to deflect saidsecond form of radiation through said transverse output aperture; and

radiation resolving means disposed between said primary and secondaryreflectors transparent to one form of radiation and reflective toanother form and concurrently passing said one form through said firstaxial output aperture and reflecting said second form through saidpassage in said secondary mirror and through said transverse outputaperture.

8. A telescope according to claim 7 wherein said barrel includes aradiation input aperture disposed to direct a beam onto the rearwardface of the deflection means and a collimating lens mounted rearward ofsaid face adapted to collimate input radiation and project a beam ofsaid input radiation through said single receiving aperture.

9. A rangin system comprising;

a telescope avmg a single ra ration receiving aperture, an axial outputaperture, a non-axial output aperture and an input aperture;

annular objective means mounted within said telescope for resolvingreceived radiation into an axial component and a non-axial componentdirected toward said axial and non-axial apertures, respectively;

infrared detecting means disposed to detect the radiation output fromone of said output apertures;

laser detecting means disposed to detect the laser radiation output ofthe other of said output apertures;

co-axial laser collimating means mounted within said telescope;

laser transmission means disposed to emit a pulse toward and throughsaid input aperture; and

ranging means associated with said laser means and laser detecting meansfor providing a signal indicative of the range of an object.

1. A multi-function telescope comprising: A housing means having anaperture for receiving a beam containing at least two forms ofradiation; means mounted within said housing means for concurrentlyresolving said beam into an axial component of one of said forms ofradiation and a non-axial component of said other form of radiation; anannular concave primary reflector and an annular obtuse secondaryreflector positioned to reflect said axial component through the bore ofsaid annular primary reflector; transmitting means coaxially disposedwithin said telescope for directing a beam of one of said forms ofradiation outward through said aperture; a non-axial aperture formed insaid telescope; a filter transparent to said axial component andreflective to said non-axial component; and a non-axial radiationdeflector disposed in a position to cause said non-axial component to bereflected axially from said filter, through the bore of said secondaryreflector onto said deflector and out said non-axial aperture of saidtelescope.
 2. A multi-function telescope comprising: A housing meanshaving a single receive aperture for receiving a beam containing atleast two forms of radiation; means mounted within said housing meansfor resolving said beam into an axial component of one of said forms ofradiation and a non-axial component of said other form of radiation; anannular primary reflector and a secondary reflector positioned toreflect said axial component through the bore of said annular primaryreflector; transmitting means coaxially disposed within said telescopefor directing a beam of one of said forms of radiation through saidreceive aperture. A non-axial aperture formed in said telescope; adichroic filter transparent to said axial component and reflective tosaid non-axial component, said secondary reflector including a centralpassage; and a non-axial radiation deflector disposed behind saidpassage in a position to cause said non-axial component to be reflectedfrom said filter, through said passage onto said deflector and out saidnon-axial aperture of said telescope.
 3. A telescope according to claim2 in which said housing comprises a cylindrical outer barrel.
 4. Atelescope according to claim 3 further including an inner barrel, meansfor mounting said secondary reflector and deflector within said innerbarrel and means for coaxially mounting said inner barrel within saidouter barrel.
 5. A telescope according to claim 4 in which said innerbarrel further includes a transmission radiation collimating lensdisposed between said deflector and receive aperture.
 6. Amulti-function telescope comprising: an optical barrel having a singlereceiving aperture; an annular primary objective reflector means mountedin the end of said barrel opposite to said aperture and said reflectorincluding a first output aperture; a secondary annular reflectordefining a central passage disposed before the image point of saidprimary reflector and adapted to reflect the radiation from the primaryreflector through the first output aperture; and radiation resolvingmeans disposed between said primary and secondary reflectors transparentto one form of radiation and reflective to another form and adapted topass said one form through said first output aperture and reflect saidsecond form through the passage in said secondary mirror.
 7. Amulti-function telescope comprising: an optical barrel having an axialreceiving aperture and a transverse output aperture; an annular primaryobjective reflector means mounted in the end of said barrel opposite tosaid receiving aperture, and said reflector including a first axialoutput aperture; a secondary annular reflector defining a centralpassage disposed before the image point of said primary reflector andadapted to reflect the radiation from said primary reflector throughsaid first axial output aperture; deflection means mounted axiallybehind said passage to deflect said second form of radiation throughsaid transverse output aperture; and radiation resolving means disposedbetween said primary and secondary reflectors transparent to one form ofradiation and reflective to another form and concurrently passing saidone form through said first axial output aperture and reflecting saidsecond form through said passage in said secondary mirror and throughsaid transverse output aperture.
 8. A telescope according to claim 7wherein said barrel includes a radiation input aperture disposed todirect a beam onto the rearward face of the deflection means and acollimating lens mounted rearward of said face adapted to collimateinput radiation and project a beam of said input radiation through saidsingle receiving aperture.
 9. A ranging system comprising: a telescopehaving a single radiation receiving aperture, an axial output aperture,a non-axial output aperture and an input aperture; annular objectivemeans mounted within said telescope for resolving received radiationinto an axial component and a non-axial component directed toward saidaxial and non-axial apertures, respectively; infrared detecting meansdisposed to detect the radiation output from one of said outputapertures; laser detecting means disposed to detect the laser radiationoutput of the other of said output apertures; co-axial laser collimatingmeans mounted within said telescope; laser transmission means disposedto emit a pulse toward and through said input aperture; and rangingmeans associated with said laser means and laser detecting means forproviding a signal indicative of the range of an object.